Severe Thunderstorm Warning 169, NWS Charleston, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
346 PM EDT FRI JUN 20 2008

.SYNOPSIS...
WEAK LOW PRES WILL MEANDER OVER THE SE U.S. THROUGH THIS WEEKEND.
FRONTAL BOUNDARY WILL LINGER NEAR OR WEST OF THE AREA INTO
MONDAY...THEN WILL DISSIPATE BY TUESDAY. A LEE SIDE TROUGH WILL
THEN PERSIST THROUGH THE MIDDLE AND LATTER PART OF NEXT WEEK AS
ATLANTIC HIGH PRESSURE REMAINS NEARBY THROUGH FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE STORM PREDICTION CENTER HAS ISSUED SEVERE THUNDERSTORM WATCH
585 FOR PARTS OF SOUTHERN SOUTH CAROLINA IN EFFECT UNTIL 9 PM EDT.
SIGNIFICANT INSTABILITY AND DEEP LAYER SHEAR WILL COMBINE TO
CREATE AN ENVIRONMENT FAVORABLE FOR STRONG TO SEVERE THUNDERSTORMS
THE REST OF THE AFTERNOON INTO THIS EVENING WITH LARGE
HAIL...DAMAGING WINDS AND TORNADOES POSSIBLE. MOST OF THE ACTIVITY
SHOULD REMAIN N OF INTERSTATE 16 IN GA.

THE STRONGEST CONVECTION SHOULD DIMINISH THIS EVENING DUE TO
NIGHTTIME STABILIZATION. HOWEVER...CANNOT RULE OUT SOME LINGERING
ACTIVITY AS WAS SEEN LAST NIGHT. THUS...HAVE MAINTAINED 20 POPS
OVERNIGHT...MAINLY ACROSS SC WHICH WILL BE CLOSER TO THE WEAK WARM
FRONT EXTENDING FROM THE AREA OF LOW PRESSURE NEAR AUGUSTA.

&&

.SHORT TERM /SATURDAY/...
WITH THE LOW PRESSURE TROUGH LINGERING OVER THE AREA SAT...EXPECT
ANOTHER ROUND OF SHOWERS AND TSTMS. WITH THIS BOUNDARY ALONG WITH
THE SEA BREEZE AND ADDITIONAL SHORTWAVE ENERGY RIDING THE BASE OF
THE UPPER TROUGH...WILL MAINTAIN HIGH END CHANCE POPS FOR MUCH OF
THE CWA N OF INTERSTATE 16 WHERE THE BEST SURFACE CONVERGENCE IS
ANTICIPATED. PLENTY OF INSTABILITY AND FAVORABLE DEEP LAYER SHEAR
WILL AGAIN PROMOTE THE POTENTIAL FOR STRONG TO SEVERE TSTMS AS
INDICATED IN THE STORM PREDICTION CENTER/S DAY TWO CONVECTIVE
OUTLOOK. WILL CONTINUE TO MENTION THIS THREAT IN THE LOCAL HAZARDOUS
WEATHER OUTLOOK /HWO/ PRODUCT.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
ONE SHORT WAVE TO MOVE THROUGH THE REGION SATURDAY NIGHT AND INTO
THE ATLC BY SUNDAY MORNING. THIS WILL RESULT IN SLOWER BOUNDARY
LAYER STABILIZATION THAN WOULD OTHERWISE BE EXPECTED...THUS WE HAVE
MAINTAINED HIGH END CHANCE POPS THROUGH MUCH OF THE NIGHT...TAPERING
OFF LATE. PRESENT INDICATIONS ARE THAT THERE WILL BE TOO MUCH CLOUD
COVER FOR ANY SIGNIFICANT FOG CONCERNS. MIN TEMPS GENERALLY WITHIN A
FEW DEGREES OF 70...EXCEPT SOME MID 70S NEAR THE IMMEDIATE COAST.

FOR SUNDAY...ANOTHER SHORT WAVE MOVES NEARBY WITHIN THE SWLY
FLOW...SKIRTING COASTAL AREAS. THIS WILL TRIGGER SCATTERED TO LIKELY
POPS...HIGHEST OVER ERN LOCATIONS. MID LEVEL LAPSE RATES ARE
POOR...CAPES ARE NO MORE THAN 500-1000 J/KG /MAINLY AS A RESULT OF
EXTENSIVE CLOUD COVER/...AND OTHER PARAMETERS SUGGEST ONLY WEAK
INSTABILITY. IN ADDITION...ATLC RIDGING MIGHT BUILD JUST ENOUGH W
THAT IT FORCES THE FRONTAL BOUNDARY TO SHIFT FURTHER W OF THE
AREA...AND ANTICYCLONIC FLOW IS ABLE TO DEVELOP. THIS CURRENTLY
POINTS TO A LOWER RISK OF SEVERE WEATHER THAN RECENT DAYS.
HOWEVER...THERE IS SOME UPPER LEVEL DIFLUENCE AND 0-6 KM BULK SHEAR
IS 25-30 KT. IF THE SEA BREEZE IS ABLE TO DEVELOP...WITH ENHANCEMENT
DUE TO THE SHORT WAVE WE STILL COULD SEE SOME ROTATING STORMS
ESPECIALLY OVER THE ERN THIRD OF THE FORECAST AREA. WITH PWATS NEAR
OR EVEN GREATER THAN 2 INCHES...LOCALIZED FLOODING WILL BE OF
CONCERN. MAX TEMPS WILL BE HELD DOWN BY PRECIP/CLOUD COVER...WITH
HIGHS MAINLY IN THE MID-UPPER 80S.

ON MONDAY...ALTHOUGH WE DO SEE THE SHORT WAVE ALOFT EXITING THE
AREA...MID LEVEL LAPSE ARE A LITTLE BETTER CLOSE TO 5.8 DEGREES
CELSIUS. CLOUD COVER DOES NOT APPEAR TO BE AS EXTENSIVE...THUS CAPE
VALUES ARE APPROACHING 2000 J/KG IN SOME LOCATIONS. TTI IS NEAR
50...K-INDEX IS GREATER THAN 35 AND LIFTED INDICES ARE NEAR -5/-6.
IN ADDITION...THE RIGHT REAR QUAD OF A 60-70 KT JET ALOFT IS FOUND
ACROSS SC...AND THE ATLC RIDGE WEAKENS A BIT AGAIN...WITH A RETURN
TO CYCLONIC FLOW AS THE FRONTAL BOUNDARY SHIFTS BACK CLOSER TO THE
FORECAST AREA. WILL LOWER POPS WITH LESS AVAILABLE MOISTURE...BUT
COULD ACTUALLY SEE A SLIGHTLY HIGHER RISK OF SEVERE WEATHER. WITH
LESS CLOUD COVER...MAX TEMPS WILL BE A FEW DEGREES HIGHER AND
REACH 90 OR BETTER IN AREAS AWAY FROM THE BEACHES.

THE MIDDLE AND LATTER PART OF THE WEEK LOOKS TO HAVE THE RETURN TO
MORE TYPICAL DIURNALLY DRIVEN T-STORMS...WITH LEE SIDE TROF W OF THE
FORECAST AREA AND ATLC RIDGING MAKING A RETURN. SEA BREEZE
CONVERGENCE ALONG WITH ANY OUTFLOW BOUNDARIES LOOK TO BE THE MAIN
DRIVING FORCE FOR CONVECTION...THUS GENERALLY SLIGHT CHANCE OR
CHANCE POPS DURING THE AFTN/EVENING DURING THE REST OF THE WEEK.
TEMPS WILL BE NEAR OR EVEN A FEW DEGREES ABOVE SEASONAL NORMALS.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
CONVECTION HAS ALREADY BEGUN TO DEVELOP OVER SC THIS AFTERNOON AND
IS EXPECTED TO CONTINUE THROUGH THE EARLY EVENING HOURS. THE
CONVECTION MAY SPREAD SWD ACROSS THE SAVANNAH RIVER BUT WE DO NOT
HAVE GREAT CONFIDENCE IN THIS. HAVE MENTION OF VCTS AT BOTH
TERMINALS AS THE SEA BREEZE PUSHES INLAND...THUS LOWERING THE
CHANCE OF SEEING ANY CONVECTION AROUND THE TERMINALS.
HOWEVER...THE STORMS THAT DEVELOP ALONG THE SEA BREEZE HAVE THE
POTENTIAL TO BUILD BACK TOWARD THE E DUE TO W WINDS ALOFT. WILL
CONTINUE TO CLOSELY MONITOR THE RADAR TRENDS AND WILL AMEND
IF/WHEN NECESSARY.

OVERNIGHT...MVFR VSBYS AT BOTH SITES ARE EXPECTED AS WINDS CALM
AND LOW LEVEL MOISTURE IS IN PLACE.

FOR SATURDAY AFTERNOON...EXPECTING ANOTHER ROUND OF POSSIBLE
CONVECTIVE FORMATION BUT THINK THE ACTIVITY WILL START BEYOND THIS
TAF FORECAST PERIOD.

EXTENDED AVIATION OUTLOOK...OCNL MVFR CONDITIONS ARE EXPECTED IN
SHRA/TSRA THROUGH MONDAY...THEN GENERALLY VFR WEATHER THE REST OF
THE WEEK.

&&

.MARINE...
TONIGHT THROUGH SATURDAY...THE SEA BREEZE ENHANCEMENT COMBINED WITH A
NOCTURNAL SURGE SHOULD KEEP WINDS 15 TO 20 KT OVERNIGHT. SEAS
WILL AVERAGE 2-3 FT THROUGH TONIGHT...ALTHOUGH MAY REACH 4 FT
BEYOND 20 NM OUT OVERNIGHT. CONDITIONS WILL REMAIN BELOW SMALL
CRAFT ADVISORY CRITERIA SAT...ALTHOUGH WINDS WILL BEGIN TO
APPROACH 20-25 KT OVER THE GA WATERS BEYOND 20 NM TOWARD THE END
OF THE PERIOD. WILL HOLD OFF ON RAISING THE ADVISORY FOR NOW AS WE
TRY TO REFINE THE TIMING.

SATURDAY NIGHT THROUGH WEDNESDAY...THE COASTAL WATERS WILL BE
SITUATED BETWEEN ATLC HIGH PRES JUST TO THE SE AND THE FRONTAL
BOUNDARY ACROSS THE SE PART OF THE COUNTRY INTO MONDAY. THE HIGH
LOOKS TO BUILD FURTHER W BEGINNING TUESDAY AS A LEE SIDE TROUGH
DEVELOPS INLAND.

S-SW WINDS WILL SURGE TO NEAR 20 KT SATURDAY NIGHT...WITH SEAS
BUILDING TO NEAR 4 OR 5 FT. AT THIS POINT WILL KEEP THE FORECAST
JUST BELOW ANY SCA CRITERIA...BUT LATER SHIFTS WILL NEED TO KEEP A
CLOSE WATCH ON AMZ330-350-374 FOR POSSIBLE SCA CONDITIONS SATURDAY
NIGHT.

WINDS TEMPORARILY COME DOWN LATER SATURDAY NIGHT INTO THE FIRST PART
OF SUNDAY...BUT PINCHING OF THE PRES GRADIENT ALONG WITH POSSIBLE
SEA BREEZE ENHANCEMENT WILL ALLOW FOR WINDS TO INCREASE AGAIN LATER
SUNDAY THROUGH MONDAY. AT THIS POINT DO NOT SEE ANYTHING HIGHER THAN
15 OR 15-20 KT...WITH SEAS GENERALLY 4 FT OR LESS.

ATLC HIGH PRES BUILDS FROM THE W ON TUESDAY AND WEDNESDAY...WITH A
MODERATE S-SW FLOW PERSISTING...ALONG WITH SOME SEA BREEZE
ENHANCEMENT NEAR THE COAST. NO HEADLINES ARE ANTICIPATED WITH WINDS
15 KT OR LESS AND SEAS 3-4 FT OR LESS DURING THIS TIME.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...SEVERE THUNDERSTORM WATCH UNTIL 9 PM EDT THIS EVENING FOR
     SCZ043>045-049-050.
MARINE...SEVERE THUNDERSTORM WATCH UNTIL 9 PM EDT THIS EVENING FOR
     AMZ330-350.

&&

RJB/33

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHARLESTON SC
325 PM EDT FRI JUN 20 2008

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0322 PM     HAIL             YEMASSEE                32.69N 80.85W
06/20/2008  E1.00 INCH       HAMPTON            SC   POST OFFICE

            QUARTER SIZE HAIL REPORTED BY A YEMASSEE POST OFFICE
            EMPLOYEE.

&&

JHP

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
339 PM EDT FRI JUN 20 2008

SCZ044-050-202030-
CHARLESTON-DORCHESTER-
339 PM EDT FRI JUN 20 2008

...STRONG THUNDERSTORMS WILL IMPACT DORCHESTER COUNTY AND CHARLESTON
COUNTY THROUGH 430 PM EDT...

AT 334 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CAPABLE OF PRODUCING SMALL HAIL...AND GUSTY WINDS
OF 30 TO 40 MPH.  THIS STORM WAS LOCATED NEAR MEGGETT...OR ABOUT 16
MILES NORTH OF EDISTO BEACH...MOVING NORTHEAST AT 15 MPH.

AREAS IN AND AROUND ADAMS RUN...HOLLYWOOD...JOHNS ISLAND...MEGGETT...
RAVENEL...WADMALAW ISLAND AND YONGES ISLAND WILL BE IMPACTED THROUGH
430 PM EDT.

BE ALERT FOR RAPIDLY CHANGING WEATHER CONDITIONS AS STORMS APPROACH.
BE READY TO TAKE IMMEDIATE ACTION IN CASE A SEVERE THUNDERSTORM
WARNING IS ISSUED FOR YOUR LOCATION.

PLEASE CONTACT THE NATIONAL WEATHER SERVICE IN CHARLESTON TOLL FREE
AT 1-888-383-2024 IF YOU OBSERVE SEVERE WEATHER SUCH AS HAIL...DOWNED
TREES...LIMBS AND POWER LINES.